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22 – Reading Resistor Colour Codes

The Resistor Colour Code is used to indicate the values or ratings of electronic resistors.  The colour code was introduced because it was easier to mark small components than to print values on them.

Normally there are three or four colour bands grouped together and then there are a bit of a space in the grouping followed by one last colour band. The first two colour bands in the group indicate the value of the resistor and the third band is the multiplier. The multiplier is used to scale up the size of the resistor. The last colour band specifies the tolerance or accuracy of the resistor. A gold band indicates a tolerance of 5% and a silver band indicates a tolerance of 10%. With a tolerance of 5% a resistor’s value can vary from -5% to +5% of the indicated value.

Colour Code Example
Using the colour code a resistor of 10 Ohm with a tolerance of 5% will have the following code, Brown, Black, Black and Gold. A resistor of 1000 Ohm with a tolerance of 5% will have a colour code of Brown, Black, Red and Gold.